>>>Back to this one - would it be fair to provide the following ROT to the
>>>OP's question:
>>>
>>>"The technical issues that caused performance concerns related to nested
>>>views in [very old] versions of Oracle are, for the largest part, no
>>>longer relevant.
>>>
>>>However, inappropriate use of views can have side effects such as
>>>unacceptable performance and resource issues. These side effects, such as
>>>unnecessary aggregation within views, could become significant in ad-hoc
>>>environments.
>>>
>>>Suitable documentation for views as well as proper analysis, including
>>>explain plans, should be considered for all 'permanent' SQL statements."
>>>
>>>FGB
>>
>>I like that - it may just be a little long for a ROT.
>>The part that sticks will probably be just the first
>>sentence, which is OK by me for a ROT.

> > > You're right - I tend to be wordy. Let's try this on for size:> > "Careless (or novice) use of nested views can have issues because of side> effects of unseen operations such as aggregations. > > Careful use of relevant and documented views should not (normally) have> performance impacts. > > Make sure you test."> > FGB
lol

That's at least one rule: test.
And perhaps another: document (what was tested).